Digital storage oscilloscope is increasingly used in time-domain measurement, and the waveform capture rate is an important indicator of performance for the data acquisition and processing of a DSO. Waveform capture rate can be defined as “the number of waveforms which an oscilloscope can capture and display in unit time”, and usually be expressed as waveforms per second (wfms/s), it indicates the size of amount of information acquired and displayed by an acquisition system in unit time. A higher waveform capture rate indicates the stronger capacity of an oscilloscope for capturing accidental event.
FIG. 1 is a diagram of waveform acquiring and processing of a DSO. As shown in FIG. 1, since the microprocessor unit (MPU) of DSO will be involved in the processing of the acquired waveform data, a time interval between two acquisitions is formed, and the time interval is called as dead time, which is from the end of previous acquisition to the beginning of next acquisition. During dead time, the acquisition system of DSO will lose the information of waveform.
The novel parallel digital storage oscilloscope, also called as digital three-dimensional oscilloscope, differs from conventional digital storage oscilloscope. The first difference is what displayed on parallel DSO is three dimensional waveform information: time, amplitude, and amplitude distribution along with the time. The second difference is the acquisition and processing of waveform data and the operation of MPU are parallel, so the dead time is greatly reduced. Although the dead time is reduced in parallel DSO, no matter how short the dead time is, it still exists. For parallel DSO, which emphasizes the capture of waveform details, the waveform capture rate is also an important indicator of performance, it determines the capacity to capture the information of waveform. Therefore, it is very necessary to measure the waveform capture rate of a parallel DSO.
We have put forward a method for measuring the waveform capture rate of a DSO, which has been granted a patent on Jun. 1, 2011 with No. CN101281224B. The method is also called as “Double Pulses Measurement”, and fills the gap of measuring the WCR of a DSO. However, with this method, only the transient waveform capture rate of a DSO can be measured, and the results just reflect the waveform capture rate at the moment of measurement.
On the basis of double pulse measurement, and considering the asymmetry of acquisition and the refreshing time of parallel DSO, the U.S. Patent Application Publication No. U.S. 2014/0188419 A1, filed by us on Oct. 18, 2013, entitled “Method for Measuring the Waveform Capture Rate of Parallel Digital Storage Oscilloscope”, herein incorporated by reference, provides a step amplitude-frequency combined pulse measurement to measure the time for waveform acquisition and mapping Tmap, the number of captured waveforms before LCD refreshing Wacq and the dead time caused by LCD refreshing TDDT, and then calculates the actual measured average waveform capture rate of a parallel DSO, according to the measured data, so that the waveform capture rate of a parallel DSO can be measured. The described “Method for Measuring the Waveform Capture Rate of Parallel Digital Storage Oscilloscope” has improved the accuracy of measuring the waveform capture rate, however, it is too many steps to proceed with. For example, when locating the position of dead time caused by LCD refreshing of Tektronix DPO4034, 27 step amplitude-frequency combined pulses are needed, the efficiency of measuring the waveform capture rate is comparatively low.